Dinah Dey/William Hillyer

I am looking for information about the children of Dinah Dey (b. 1730) and William Hillyer (b. 1728). Using information that has come through my family and what I have found on the Dye Scoiety web page, I think that Dinah Dey is the daughter of James Dey and his first wife Dinah Tillyer (Hillyer?). James Dey being the son of James Hans Dey and his second wife Margaret. Dinah Dey's husband Wiliam was the son of Elizabeth Dey and John Hillyer, with Elizabeth being the daughter of the same James Hans Dey and his first wife Mary.

The family information I have indicates that William and Dinah had a child in 1849, but everything I have found shows that they weren't married until 1755. Can anyone help clear this up? Many thanks.